This invention relates to improvements in skids for supporting rotating machinery.
There are applications where it is required to support heavy machinery on a base in such a manner that all loads are adequately supported and any substantial torque, including that generated by the instantaneous failure of a driven part, can be resisted and in such locations where the machinery may be exposed to severe external forces.
One such application with which the present invention is particularly, but not exclusively, concerned is where the machinery is an electrical generator for an oil rig. For example, such machinery can take the form of a gas generator such as an Avon gas generator driving a power turbine which in turn drives an electrical generator through a gear box and can weigh of the order of 85,000 lbs. Such an electrical generator can be designed to produce electrical power of the order of 9 MW and failure of the electrical generator due, for example, to a short-circuit, results in an extremely high torque which, although short-lived due to the consequent operation of circuit-breakers, nevertheless has to be absorbed. Such machinery on an oil rig could be exposed to winds of the order of 125 mph and the base on which it is mounted and which forms part of the rig structure can expand and contract due to thermal variations and be exposed to mechanical forces generated in the rig structure.
Conventionally, such machinery is mounted on a base frame or skid which is secured to a deck of the rig by bolts after being levelled by shim-plates or packings and which is composed of beams, e.g., of I-section and H-section dimensioned to withstand the high stresses and forces involved. Such a base frame, being designed for maximum strength is unduly heavy and yet nevertheless in use, and even under its own weight in transportation to site can deform to an extent to produce misalignment between the design axes for the drive shafts between the turbine and the gear box and the generator with consequent significant problems in installing the machinery or in replacing a part of the machinery in use on the rig.